The Developmental Consequences of a Chick Embryo Between 24 Hours and 72 Hours

To study the developmental biology of a chick embryo the first step is to collect a fertilized egg. These eggs are available from a hatchery or poultry farm. Then the fertilized eggs must be incubated in the incubator apparatus of a laboratory. When the desired time of incubation is done then the embryo must be extracted out and will be fixed by a fixative. It may be followed by staining procedure directly for the preparation of whole mount.

PROCEDURE :

a) The incubated egg at first is carefully cleaned by a cotton wool soaked with 50 % alcohol.

b) After that the egg is gently massaged with palm for at least 7 minutes.

c) The outer shell is then should be cracked at the broader end with the help of a scalpel and by this way the shell will be removed from that end.

d) Then the outer and inner shell membranes are to be removed by forceps.

e) The embryo is now to be spotted and few drops of FAA is added on it to fix it in situ. (FAA is a solution of Formalin, 90 % alcohol and acetic acid.)

f) After one minute the embryo is to be taken out from the egg scissoring the membrane at the embryo's margin.

g) Now the embryo must be transferred to the fresh FAA and to be kept for 30-45 minutes.

h) It is then to be passed through 70 % alcohol for three minutes and 90 % alcohol for five minutes.

i) Now the embryo is to be stained with Eosin for 3-5 minutes and then washed in 90 % alcohol.

j) Then, it must be dehydrated in 100 % alcohol.

k) This is then should be mounted with DPX over the slide.

THE ANATOMICAL FEATURES OF 24-HOUR CHICK EMBRYO :

1. Two subdivisions of Area Opeca i.e. Area Vitellina and Area Vasculosa can be distinguished.

2. Hensen's Node is distinct.

3. There is no somite is present.

4. The clear head fold is anteriorly present.

5. Primitive streak is widened from posterior part.

6. Area Vasculosa is with traces of yolk.

7. At the cephalic region neural fold is present.

THE ANATOMICAL FEATURES OF 32-HOUR CHICK EMBRYO :

1. Three major divisions of brain i.e. Procencephalon, Mesencephalon and Rhombencephalon are distnguisable.

2. Notochord is distinct.

3. There are 10 pairs of somites and elongated foregut is present.

4. Outgrowth of Optic vesicle is present and heart is found at the nearly right part.

5. Well developed Vitelline vein is present and Mesoderm is unsegmented.

THE ANATOMICAL FEATURES OF 48-HOUR CHICK EMBRYO :

1. 27-30 pairs of somites are present.

2. Optic cup is totally formed.

3. Tail bud is developed.

4. Both cranial and cervical flexures are developed.

5. Otocyst is clear and three pairs of arterial arches are originated from the ventral aorta.

THE ANATOMICAL FEATURES OF 72-HOUR CHICK EMBRYO :

1. Well formed Spinal cord.

2. Cranial flexure is very distinct.

3. Olfactory placode is well developed.

4. Lens formed in the optical vesicles.

5. In heart, well developed atrium and ventricle are present.

6. Pharyngeal pouches and Aortic arches are well developed.